1. Field of the Invention
The present invention relates to a magnetic head in which one of mutually abutting core members is notched deeper than the other.
2. Description of the Prior Art
The so-called Philips-type tape cassette is provided with three larger apertures principally for receiving magnetic heads or pinch roller and two smaller apertures for receiving sensors or the like. However, in recent highly advanced tape recorders for example having dual capstans and automatic reversing functions, the erasing magnetic head has to be inserted into one of said smaller apertures. For this reason a magnetic head having a protruding structure in the tape contacting portion has been employed. FIG. 1A shows, in a perspective view, the interior of a conventional erasing magnetic head utilizing the aforementioned smaller aperture in which a head element 7, composed of a center core member 1, a coil 2 side core members 3, 4 (forming magnetic gaps 5a, 5b) and a block 6 are mounted on a holder 10 having terminals 9a, 9b to which the wires 8a, 8b of said coil 2 are connected.
FIG. 1B is a lateral view of the head element 7 seen from the direction of arrow A in FIG. 1A, while FIG. 1C is a plan view of said element seen from the direction of arrow B in FIG. 1A. The head element 7 has to be extremely compact in order to be insertable into the smaller aperture of the cassette, so that the lateral dimension W of the protruding core has to be limited as shown in FIG. 1A, with the reduced cross sections of the center core member 1 and the side core members, 3, 4. Such reduced cross sections of the core members result in a magnetic saturation of the magnetic circuit composed of said core members when a large current is applied to the coil 2.
For this reason, in the conventional magnetic head, the core height T2 is selected larger than the track width T1 to enlarge the cross section of the magnetic circuit, and the tape contacting portion of the center core member 1 and the core members 3, 4 are partially notched to meet the track width, the notch 6a being filled with the block 6 which is plate-shaped and non-magnetic. However the structure shown in FIGS. 1A to 1C is still defective in giving rise to saturation of magnetic circuit and leaking magnetic flux between the core members when the flux density around the magnetic gaps is elevated, thus leading to an elevated distortion as explained afterwards.